It wasn't really difficult. I just activated the ingame debug mode and saw that the problem is in line 409 of moth.lua. Then i opened it and via google i found out, that the function in this line doesn't exist anymore in the API. So i just deleted the line and it worked. This could have done by anyone else, as i don't have any coding knowledge at all.
We should all thank the creator of this addon (or any addon). I think the difference between this fix and creating the addon is as big as the difference between watching at a mountain and climbing on it.
Also we should thank the devs who rebuild the server, as this is even a bazillion times harder then creating an addon.